1. Field of the Invention
The present invention relates to an image display system comprising an image supply device and a projector connected via a network, and particularly relates to an image display system that is suitable for displaying of moving images.
2. Description of the Related Art
In the past, a projector for which a personal computer (hereafter abbreviated as “PC”) which is an image supply device and a projector are connected via a network, and that is able to supply and display an image from the PC to the projector (hereafter called a “network projector”) was proposed (e.g. see International Publication Pamphlet No. 01/093583).
Also, an art called VNC (Virtual Network Computing) is used to supply images from a PC via a network to this kind of network projector.
However, with VNC, of the images generated by the image supply device, image data of the area for which the image has changed (change area) (e.g. bit map data or JPEG data) is transferred. Because of this, when the size of the change area is large and the data volume of the image data to be transferred is large, there is the problem that the network traffic increases, and the response worsens.
For example, compared to a case of displaying a moving image at a certain screen size (hereafter called “standard screen size”), when displaying a moving image on a screen size that is expanded bigger than the standard screen size (hereafter also called the “expanded screen size”), the data volume per frame of the moving image becomes greater. Because of this, when displaying a moving image at the expanded screen size, the data volume required for realizing a real time moving image display is increased compared to when displaying a moving image at the standard screen size. As a result, when displaying a moving image at the expanded screen size, if the network data transmission speed is fixed, the number of frames of a moving image that can be displayed per unit of time will be less than when displaying a moving image at the standard screen size, and there are cases when real time moving image display is not possible.